Device for casting strands of metal

ABSTRACT

The invention is directed to a device for casting strands of metal, in particular steel, with a material supply vessel, the liquid metal being delivered to the carrying side of a circulating conveyor belt by means of the pouring nozzle of the material supply vessel. The conveyor belt comprises a thin, heat-resistant belt which circulates between a first deflection roller and a second deflection roller and which is shaped after the first deflection roller and in the region of the outlet nozzle to form a trough for receiving the liquid metal and resumes the shape of a flat belt in proximity to the second deflection roller. In order to reduce stresses on the belt, it is proposed that at least one of the deflection rollers is cambered in a convex manner.

PRIORITY CLAIM

This is a U.S. national stage of Application No. PCT/DE2008/000031,filed on 8 Jan. 2008, which claims Priority to the German ApplicationNo.: 10 2007 010 578.0, filed: 26 Feb. 2007 the contents of both beingincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to a device for casting strands of metal, inparticular steel, with a material supply vessel, the liquid metal beingdelivered to the carrying side of a circulating conveyor belt by apouring nozzle of the material supply vessel, wherein the conveyor beltcomprises a thin, heat-resistant belt that circulates between a firstdeflection roller and a second deflection roller, the conveyor belt isshaped after the first deflection roller in a region of the pouringnozzle to form a trough for receiving the liquid metal and the conveyorbelt resumes a flat shape in proximity to the second deflection roller.

2. Prior Art

A device of the type mentioned above is known from Japanese Publication59147755 A, in which the trough shape of the belt is achieved byvertical and horizontal conveying rollers arranged along the conveyingpath between the two deflection rollers and act on the belt.

SUMMARY OF THE INVENTION

Due to the relatively large differences in temperature along a width ofthe belt that act on the belt through the liquid metal and because ofthe deformation of the belt from a flat shape to the trough shape andthen back again into the flat belt shape, there are widely varyingchanges in length along the width of the belt resulting in criticalstresses on the belt material, particularly in the edge area.

Although the belt—usually a steel belt for this purpose—has anelasticity corresponding to the belt material that is used, acost-effective lifetime cannot be achieved as a result of the differentstresses on the belt along the width.

Therefore, it is an object of the invention to design the device suchthat the stresses on the belt are reduced and evened out. Further, newmaterials are used for the belt material because of the reduced, moreuniform stress on the belt. Further, the entry length and exit lengthare adapted to the geometry of the trough profile for specificadjustment of the degree of camber. This increases the costeffectiveness of the casting process appreciably.

The above-stated object is met according to one embodiment of theinvention in that at least one of the deflection rollers is cambered ina convex manner.

Owing to a deliberate cambering of at least one of the deflectionrollers, by which the shortening of the belt resulting from theformation of the trough profile is at least partially compensated andbecause the different temperature distribution along the width of thebelt is also taken into consideration in the camber, the stress on thebelt is made homogeneous, which has a positive impact on the life of thebelt.

It is advantageous when the camber of at least one of the deflectionrollers is varied by a pressure medium to compensate for the change inlength, e.g., due to modified casting parameters. To this end, aprofiled cavity is provided in the roller shell. In this connection, itcan also be advantageous when the camber of the first deflection roller,is smaller than that of the second deflection roller.

The camber can be calculated based on the geometry of the troughprofile. The average trough profile is used for the calculation when thetrough profile varies over the length of the trough to adapt to theshrinkage of the casting profile.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic side view of the belt with the deflection rollersin a side view;

FIG. 2 is a cross section through the trough shape

FIG. 3 is a calculation model with a simplified trough shape as arectangular shape for the calculation and cambering of the deflectionroller; and

FIG. 4 is a trough cross section for calculating the influence oftemperature.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a belt 10 and deflection rollers 12 and 14. Asshown, pouring nozzle 16 is configured to supply liquid metal to thebelt 10 in an area between rollers 12 and 14. The belt 10 is shaped suchthat a portion of the area between the rollers 12 and 14 istrough-shaped. At least one of the rollers 12, 14 is convexly cambered.

The camber of the rollers 12, 14 is a function of the respective entrybelt length Le and exit belt length La between the deflection roller andthe trough profile (FIG. 1) or, conversely, of the belt width B_(B),trough width B_(T), trough height H_(T) and trough profile (FIG. 2),where a rectangular longitudinal shape is assumed for purposes of thecalculation.

The camber is yielded by: f(Le or La,B_(B),B_(T),H_(T), trough profile).

The calculation of the camber is preferably carried out for every pointof the deflection roller between points A and B of the trough profilewith coordinates X and Y and length Le (a) for half of the belt widthB_(B) between points C and D, shown in FIG. 3. The calculation of thecamber is carried out for the entry side and the exit side.

The calculation of the different belt length owing to the varyingtemperature distribution over the width of the belt is carried out in asimplified manner according to the indicated formula. For an exactcalculation, the temperature profile over the width of the belt iscalculated corresponding to the casting parameters.

By means of the two formulas, the optimum camber of the deflectionrollers for homogenized tensile stress over the width of the belt can becalculated for a given trough profile (casting format) and temperatureprofile by superposition:

B _(B)/2=X _(B) +X+X _(T)  (1)

ΔL _(XB) =L−L _(V)=√{square root over (L ² +X ² +Y ²)}  (2)

Δl _(Temp) =L _(Trough)α(T _(M) −T _(R))  (3)

where

-   -   B_(B) is the width of the belt (FIG. 3)    -   B_(T) is the width of the trough (FIG. 3)    -   H_(T) is the height of the trough (FIG. 3)    -   L is the length of the (final) trough profile between the entry        and exit (FIG. 1)    -   Le is the entry length from the center of the first deflection        roller to the final trough profile (FIG. 1)    -   La is the exit length from the final trough profile to the        center of the second deflection roller (FIG. 1)    -   L_(V) is the length of the space diagonal in longitudinal        direction of the trough (FIG. 3)    -   X is the X coordinate for calculating L_(V) (FIG. 3)    -   X_(T) is the distance from the center of the belt or trough to        the side of the trough (FIG. 3)    -   X_(B) is the distance from point C to X_(L)+x from the center of        the belt (FIG. 3)    -   Y is the Y coordinate for calculating L_(V) (FIG. 3)    -   T_(M) is the temperature in the center of the belt (FIG. 4)    -   T_(R) is the temperature at the edge area of the belt (FIG. 4)    -   α is the coefficient of expansion of the belt material    -   β is the angular deviation from the vertical (FIG. 2)

The camber of the first deflection roller 14 is preferably smaller thanthat of the second deflection roller 12.

The camber should be changeable, e.g., by a pressure medium, in at leastone of the deflection rollers 12, 14. To this end, a profiled cavity canbe provided at the roller shell for applying pressure.

The entry length and exit length, respectively, should preferably begreater than 500 MM.

The maximum entry length or exit length is selected in such a way thatthe camber due to the trough profile is not greater than 2%.

The belt is preferably shaped by the deflection roller continuously overthe distance Le or La to form the trough profile or flat belt.

A particularly suitable belt material is a thermal shock-resistant alloybased on CuNi, Fe.

The belt material can be made of a single-phase or multiple-phase Cualloy or a nickel-based alloy.

The belt 10 preferably has a thickness from about 0.5 mm to about 2.0mm.

The trough profile should have the shape of an arc and is preferablysymmetrical.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepswhich perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

1-21. (canceled)
 22. A device for casting strands of metal, the devicecomprising: an outlet nozzle configured to supply liquid metal from amaterial supply vessel; a circulating conveyor belt assembly beingconfigured to receive the liquid metal from the outlet nozzle on acarrying side, the conveyor belt assembly comprising: a first deflectionroller; a second deflection roller; and a thin, heat-resistant belt thatcirculates between the first deflection roller and the second deflectionroller, the belt being shaped to form a trough for receiving the liquidmetal between the first deflection roller and the second deflectionroller in a region of the outlet nozzle, the circulating conveyor beltresuming the shape of a flat belt proximate to the second deflectionroller, wherein at least one of the first deflection roller and thesecond deflection roller is convexly cambered.
 23. The device accordingto claim 22, wherein the camber is selected such that a shortening ofthe belt resulting from the formation of the trough profile is at leastpartially compensated.
 24. The device according to claim 22, wherein thecamber is calculated according to the following formulae:B _(B)/2=X _(B) +X+X _(T)  (1)ΔL _(XB) =L−L _(V)=√{square root over (L ² +X ² +Y ²)},  (2) whereinB_(B) is a width of the belt B_(T) is a width of the trough, L is alength of a final trough profile between an entry and exit, L_(V) is alength of a space diagonal in longitudinal direction of the trough, X isan X coordinate for calculating L_(V), X_(B) is a distance from point C,X_(T) is a distance from a center of the belt or trough, Y is a Ycoordinate for calculating L_(V).
 25. The device according to claim 24,wherein a change in belt length due to varying temperature distributionover a width of the belt is taken into account in the camber and iscalculated according to the following formula:Δl _(Temp) =L _(Trough)α(T _(M) −T _(R)),  (3) wherein L_(Trough) is alength of the trough, T_(M) is a temperature in a center of the beltT_(R) is a temperature at an edge area of the belt, and α is acoefficient of expansion of a belt material.
 26. The device according toclaim 25, wherein the camber of the deflection rollers for a homogenizedtensile stress over the width of the belt is calculated for a giventrough profile and temperature profile by superposition.
 27. The deviceaccording to claim 26, wherein a first deflection roller camber issmaller than a second deflection roller camber.
 28. The device accordingto claim 22, wherein the camber is changable by a pressure medium in atleast one of the deflection rollers.
 29. The device according to claim28, wherein a profiled cavity is provided at a roller shell for applyingpressure.
 30. The device according to claim 22, wherein each of a beltentry length and a belt exit length is at least 500 mm.
 31. The deviceaccording to claim 30, wherein at least one of a maximum belt entrylength and a maximum belt exit length is selected such that the camberdue to the trough profile is not greater than 2%.
 32. The deviceaccording to claim 22, wherein the belt is shaped by the deflectionroller continuously over a distance to form at least one of the troughprofile and flat belt.
 33. The device according to claim 22, wherein thebelt material comprises a thermal shock-resistant alloy comprising atleast one of CuNi and Fe.
 34. The device according to claim 22, whereinthe belt material comprises a single-phase or multiple-phase Cu alloy.35. The device according to claim 22, wherein the belt materialcomprises a nickel-based alloy.
 36. The device according to claim 22,wherein the belt has a thickness greater than about 0.5 mm and less thanabout 2.0 mm.
 37. The device according to claim 32, wherein the troughprofile is arc-shaped.
 38. The device according to claim 32, wherein thetrough profile is symmetrical.
 39. The device according to claim 32,wherein the trough profile has substantially straight-line regions atboth ends.
 40. The device according to claim 32, wherein sides of thetrough profile are higher than the casting profile by about 10 mm. 41.The device according to claim 40, wherein the sides have an angulardeviation of +/−25 degrees relative to a perpendicular of the belt whenflat.
 42. The device according to claim 32, wherein the trough profileis adapted to shrinkage of a casting cross section by an adjustment ofthe rollers in casting direction over the length of the trough.
 43. Thedevice according to claim 22, wherein a change in belt length due tovarying temperature distribution over a width of the belt is taken intoaccount in the camber and is calculated according to the followingformula:Δl _(Temp) =L _(Trough)α(T _(M) −T _(R)),  (3) wherein L_(Trough) is alength of the trough, T_(M) is a temperature in a center of the beltT_(R) is a temperature at an edge area of the belt, and α is acoefficient of expansion of a belt material.